Protective helmet



FIG. 1 is a perspective view of a protective helmet showing my new design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a side elevation view thereof, the opposite side being a mirror image;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a rear elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof. 

I claim the ornamental design for a protective helmet, as shown and described. 